Continuous casting mold for liquid metals, especially for liquid steel

ABSTRACT

The invention relates to a continuous casting mould for liquid metals, especially for liquid steel, comprising steel charging plates ( 2 ) which are surrounded by water reservoirs ( 1 ), cassette-type copper plates ( 3 ) arranged against the same, end plates ( 7 ), if needed, for the thickness and/or the width of the cast billet, and coolant channels ( 9 ). The aim of the invention is to take measures to counteract the high temperatures in the meniscus region ( 13 ) using appropriate embodiments of the copper plates ( 3 ) and/or the steel charging plates ( 2 ). To this end, the thickness ( 10 ) of the copper plates ( 3 ) between the coolant ( 11 ) and the hot side ( 3 a) of the copper plates varies along the width (2×L) and/or in terms of the height ( 12 ).

The invention concerns a continuous casting mold for liquid metals,especially liquid steel, with steel charging plates, which are arrangedparallel opposite each other to form the casting cross section and aresurrounded by water tanks; with cassette-type copper plates, which restagainst the steel charging plates and bound the casting cavity; possiblywith end plates, which are inserted at the end faces of the castingcavity for establishing the thickness and/or width of the cast strandand close the casting cavity at the end faces; and with coolant channelsthat connect an inlet with an outlet in the copper plates at theircontact surfaces with the steel charging plates.

The specified continuous casting mold is known from DE 195 81 604 T1. Acontinuous casting mold of this type represents a so-called cassettemold. The cassette mold has cassette-like copper plates that restagainst the steel charging plates and bound the casting cavity. Inprinciple, it has the advantages that fewer water tanks are needed, thatshorter changing times for the cassette-like copper plates arenecessary, that conveyance costs are lower due to the lower conveyanceweight, and that the service life of molds of this type are longer.Despite these advantages,. the cassette mold has the disadvantage of ahigh hot-side temperature in the meniscus region with a sharptemperature drop below it. This results in a high load of the strandshell on the cast strand and thus the danger of surface defects. Inaddition, an uneven slag film thickness develops prematurely due to thesignificantly different hot-side temperature in the upper region of themold.

Furthermore, it must be assumed on the basis of experience thatdifferent mold temperatures are also present along the cast width, whichcan have a negative effect on the service life of the mold and thesurface quality of the cast strand.

The objective of the invention is to propose measures that counteractthe high temperatures in the meniscus region of a cassette mold of thistype by suitable design of the copper plates and/or the steel chargingplates.

In accordance with the invention, this objective is achieved by varyingthe thickness of the copper plates between the coolant and the hot sideof the copper plates over the width and/or over the height. In this way,the hot-side temperature can be evened out over the width of the mold,and the significant temperature drop below the meniscus region can bereduced over the height of the mold.

In one embodiment, the coolant channels run in the copper plate and atleast partially in the adjacent steel charging plate. On the one hand,this guarantees equal flow rates in the coolant channels and, on theother hand, the production of the coolant channels in the copper plateand in the steel charging plate is greatly simplified.

The improved heat dissipation in the meniscus region can be stillfurther improved by making the cross section of the coolant channelsmaller in the meniscus region than elsewhere in the coolant channel.

In another measure for reducing the hot-side temperature in the meniscusregion, the thickness between the coolant channel and the hot-sidesurface of the copper plate is smaller than it is above and below thisregion.

Temperature equalization between higher and lower regions within theheight of the continuous casting mold is further promoted by limitingthe smaller thickness between the coolant channel and the hot-sidesurface of the copper plate to a certain height section and continuouslyincreasing the thickness to a certain distance in lower sections.

When the coolant channels are suitably incorporated in the steelcharging plate, it is provided that the distance of the hot-side surfaceof the copper plate from the coolant channel is constant in the sameheight sections.

The arrangement of the coolant channels generally depends on theinterior shape of the casting cavity. To this end, it is proposed thatin the width section, the distance to the hot-side surface is smaller inthe central region than in the peripheral region. This makes it possibleto make the temperature of the hot side more uniform.

For this purpose, it is further proposed that grooves in the copperplate which communicate with the coolant channel are formed with groovedepths greater than 10 mm and less than 25 mm.

Special molds for casting thin slabs are used in CSP plants. Here it isadvantageous that a funnel mold can be used and that the width sectionwith the greatest distance of the coolant channel from the hot-sidesurface of the copper plate has a length of 50-80% of the width regionin the funnel.

In accordance with additional features, an external width region of thefunnel cross section is 50-80% of the wide-side length “L” minus halfthe width of the funnel.

Specific embodiments of the invention are illustrated in the drawingsand are described in greater detail below.

FIG. 1 shows a vertical center cross section through the continuouscasting mold.

FIG. 2 shows a vertical partial cross section through the copper platewith the steel charging plate.

FIG. 3 shows the same cross section as FIG. 2 for an alternativeembodiment.

FIG. 4 shows a top view of a wide side of a mold designed as a funnelmold.

In the continuous casting mold, liquid metals, especially liquid steel,are cast into cast strands with various formats and with billet, bloom,slab, and thin-slab cross sections. Opposing steel charging plates 2 andcopper plates 3 that rest against the steel charging plates 2 aremounted inside a water tank 1, e.g., fastened with screws 4 to the steelcharging plates 2, which form a cassette. The copper plates 3 bound thecasting cavity 5. End plates 7, so-called narrow-side plates, arearranged between the copper plates 3. The thickness 8 of the end plates7 forms the thickness of the cast strand, or the end plates 7 determinethe width of the cast strand by the distance that separates them.

Coolant channels 9, each of which is provided with an inlet and anoutlet, are incorporated in the copper plates 3 at the boundary with thesteel charging plates 2.

In contrast to previous mold copper plates 3, the thickness 10 of thecopper plates 3 between the coolant 11 and the hot side 3 a of thecopper plates 3 varies over the width 2×L and/or over the height 12 ofthe mold. In the region of the meniscus 13, the thickness 10 of thecopper plate 3 is kept smaller than in the deeper, larger region, sothat the heat dissipation in the meniscus region 13 is significantlygreater than in the deeper region. This results in the establishment ofa lower hot-side temperature in the meniscus region.

As is indicated in FIG. 1 by the broken line, the coolant channels 9 inthe copper plate 3 can also run at least partially in the adjacent steelcharging plate 2.

In the region of the meniscus 13 (FIG. 2), the copper plate 3 is keptuniformly thick, and the coolant channels 9 are also uniformly deep.Accordingly, a narrower coolant channel 9 is designed normally throughan opposing steel charging plate 2 at a height H1 at the meniscus 13 andmore narrowly at the height H2 below it, so that the desired higher flowrate of the coolant 11 is produced between the copper plate 3 and thesteel charging plate 2 at height H2. The coolant 11 can be conveyedalternatively from top to bottom or from bottom to top. A smaller crosssection 14 of the coolant channel 9 is thus obtained at the height H2.In a practical embodiment, the height H1 can be 40-90 mm, and the heightH2 can be 80-150 mm.

The coolant channel cross section 14 (FIG. 3) is designed with minimumthickness (A_(min)) at height H2. In the lower regions, the coolantchannel cross section 14 is continually larger, and the lower region ofthe thickness (A_(u)) of the copper plate 3 is also designed continuallylarger.

Furthermore, in the meniscus region 13, the thickness 10 of the copperplate 3 between the coolant channel 9 and the hot-side surface 3 a ofthe copper plate 3 is the same at the top and the bottom in FIG. 2, butin FIG. 3, this thickness 10 is small at the top and larger at thebottom.

The smaller thickness 10 between the coolant channel 9 and the hot-sidesurface 3 a of the copper plate 3 is limited to the height section H2.This smaller thickness 10 between the coolant channel 9 and the hot-sidesurface 3 a of the copper plate 3 increases continuously to the distanceA_(u), in the sections below the height section H2.

As shown in FIG. 4, the copper wall thickness of a funnel mold 17 infront of the coolant and/or the cooling groove geometry (depth, width,diameter, and distance) varies over the mold width 2×L. Thisadditionally evens out the hot-side temperature over the mold width 2×L,and the significant temperature drop below the meniscus region 13 canalso be reduced over the height 12 of the mold.

In this regard (FIG. 4), a distance D1, D3 of the hot-side surface 3 aof the copper plate 3 is held constant in the same width sections L1,L3. In addition, in the same width sections L1, L2, L3, starting fromthe width sections L1, L3 with the distances D1, D3, a distance D2 inthe width section L2 is reduced to a dimension D2 towards the centralregion. Grooves 15 that communicate with the coolant channel 9 areformed in the copper plate 3 with groove depths greater than 10 mm andless than 25 mm.

When a funnel mold 17 (for CSP plants) is used, the width section L3with the greater distance D3 of the coolant channel 9 from the hot-sidesurface 3 a of the copper plate 3 has a length of 50-80% of the lengthregion L in the funnel 17 a.

An external width region L1 of the copper plates 3 is 50-80% of thewide-side half-length L minus the funnel half-width L3.

The grooves 15 in the width section L1 with the distance D_(Cu1) and thegroove depth D_(P11) are the same as in L2 with D_(Cu2)+D_(P12) and thesame as in L3 with D_(Cu3)+D_(P13). The total groove depth is less than20 mm and greater than 10 mm.

The width sections L are to be dimensioned with L1=0.5-0.8 (L−T_(F)/2),L2=L−(L1+L3), and L3=0.5-0.8 T_(F)/2, where T_(F)/2 is half the funnelwidth.

List of Reference Symbols

-   1 water tank-   2 steel charging plate-   3 copper plate-   3 a hot-side surface-   4 screws-   5 casting cavity-   6 end face-   7 end plates-   8 thickness of the end plate-   9 coolant channel-   10 thickness of the copper plate-   11 coolant-   12 height of the mold-   13 meniscus (region)-   14 coolant channel cross section-   15 grooves-   16 groove depth-   17 funnel mold-   17 a funnel-   L half the mold plate width-   L1, L2, L3 width sections-   D_(Cu1), D_(Cu2), D_(Cu3) distances in the copper-   D_(P11), D_(P12) , D_(P13) groove depth-   T_(F) groove cross section

1. Continuous casting mold for liquid metals, especially liquid steel,with steel charging plates, which are arranged parallel opposite eachother to form the casting cross section and are surrounded by watertanks; with cassette-type copper plates, which rest against the steelcharging plates and bound the casting cavity; possibly with end plates,which are inserted at the end faces of the casting cavity forestablishing the thickness and/or width of the cast strand and close thecasting cavity at the end faces; and with coolant channels that connectan inlet with an outlet in the copper plates at their contact surfaceswith the steel charging plates; characterized by the fact that thethickness (10) of the copper plates (3) between the coolant (11) and thehot side (3 a) of the copper plates (3) varies over the width (2×L)and/or over the height (12) of the mold.
 2. Continuous casting mold inaccordance with claim 1, characterized by the fact that the coolantchannels (9) run in the copper plate (3) and at least partially in theadjacent steel charging plate (2).
 3. Continuous casting mold inaccordance with claim 1 or claim 2, characterized by the fact that thecross section (14) of the coolant channel (9) is smaller in the meniscusregion (13) than elsewhere in the coolant channel (9).
 4. Continuouscasting mold in accordance with claim 1 or claim 2, characterized by thefact that the thickness (10). between the coolant channel (9) and thehot-side surface (3 a) of the copper plate (3) is smaller in themeniscus region (13) than it is above or below this region. 5.Continuous casting mold in accordance with claim 3 or claim 4,characterized by the fact that the smaller thickness (10) between thecoolant channel (9) and the hot-side surface (3 a) of the copper plate(3) is limited to the height section (H2), and the thickness increasescontinuously to a distance (A_(u)) in lower sections.
 6. Continuouscasting mold in accordance with any of claims 1 to 5, characterized bythe fact that a distance (D1; D3) of the hot-side surface (3 a) of thecopper plate (3) is constant in the same height sections (L1; L3). 7.Continuous casting mold in accordance with any of claims 1 to 6,characterized by the fact that in width section (L2), the distance tothe hot-side surface (3 a) is smaller in the central region than in theperipheral region.
 8. Continuous casting mold in accordance with any ofclaims 1 to 7, characterized by the fact that grooves (15) in the copperplate (3) which communicate with the coolant channel (9) are formed withgroove depths (16) greater than 10 mm and less than 20 mm.
 9. Continuouscasting mold in accordance with any of claims 1 to 8, characterized bythe fact that a funnel mold (17) can be used and that the width section(L3) with the greatest distance (D3) of the coolant channel (9) from thehot-side surface (3 a) of the copper plate (3) has a length of 50-80% ofthe width region (L) in the funnel (17 a).
 10. Continuous casting moldin accordance with claim 9, characterized by the fact that an externalwidth region (L1) of the copper plate (3) is 50-80% of the wide-sidehalf-length (L) minus the funnel half-width (L3).